dt-bindings: mmc: meson-gx: add optional power-domains

On newer SoCs, the MMC controller can require a power-domain to operate,
add it as optional.
Signed-off-by: Neil Armstrong <neil.armstrong@linaro.org>
Acked-by: Rob Herring (Arm) <robh@kernel.org>
Link: https://lore.kernel.org/r/20240605-topic-amlogic-upstream-bindings-fixes-power-domains-mmc-v1-1-4acbb8cc2626@linaro.orgSigned-off-by: Ulf Hansson <ulf.hansson@linaro.org>

Documentation/devicetree/bindings/mmc/amlogic,meson-gx-mmc.yaml

@@ -51,6 +51,9 @@ properties:
       set when controller's internal DMA engine cannot access the DRAM memory,
       like on the G12A dedicated SDIO controller.
 
+  power-domains:
+    maxItems: 1
+
 required:
   - compatible
   - reg